Numeric Nutrient Criteria: What Does That Mean?
In a precedent-setting action for the rest of the nation, EPA has issued numeric nutrient criteria (NNC) for Florida waters. While numeric effluent limits have been commonly used for other types of pollutants, narrative criteria have always been used to determine the health of a waterbody in Florida. The switch to numeric criteria will have far-reaching impacts on the state, its local governments, and the private sector.
The final NNC standards set numeric limits on the amount of total nitrogen (TN) and total phosphorus (TP) allowed in Florida’s Waters of the State. This action seeks to improve water quality and to protect public health, aquatic life, and the long-term recreational uses of Florida’s waters. The rule will take effect on March 6, 2012, except for the site-specific alternative criteria (SSAC) provision allowing a community to propose and justify alternative waterbody classification standards, which became effective February 4, 2011.
Pursuant to a January 2009 Clean Water Act determination and a consent decree with Florida Wildlife Federation to settle a 2008 lawsuit, EPA adopted numeric nutrient water-quality standards in December 2010 for lakes and flowing waters in Florida. EPA also committed to propose numeric nutrient water-quality standards for Florida’s estuarine coastal and southern inland flowing waters by November 14, 2011, and establish these final standards by August 15, 2012.
Florida currently uses a narrative nutrient standard to guide the management and protection of its waters. Chapter 62-302.530, Florida Administrative Code (FAC), states “in no case shall nutrient concentrations of a body of water be altered so as to cause an imbalance in natural populations of flora or fauna.”
Anticipating EPA’s actions, the Florida Department of Environmental Protection (FDEP) has been actively working with EPA on the development of FDEP numeric nutrient criteria for several years. FDEP submitted its initial “DRAFT Numeric Nutrient Criteria Development Plan” to EPA Region 4 in May 2002, and received mutual agreement on the Numeric Nutrient Criteria Development Plan from EPA on July 7, 2004. FDEP revised its plan in September 2007 to more accurately reflect its evolved strategy and technical approach, and FDEP received mutual agreement on the 2007 revisions from EPA on September 28, 2007. On January 14, 2009, EPA formally determined that numeric nutrient criteria should be established on an expedited schedule and issued its own criteria ahead of FDEP’s rulemaking.
Waterbody biological ecosystem responses are complicated, making regulations for these systems necessarily complex. Recognizing geological and temporal variations across Florida, EPA has developed rules for three types of waterbodies (lakes, flowing waters, and estuaries) and four broad regions of the state. The rules also address criteria for the particularly difficult issue of water quality in the south Florida canals. Acknowledging the naturally occurring high levels of color and varying alkalinities in many waterbodies, there are also criteria for three levels of color and alkalinity (Tables 1 and 2). Provisions for further subdivision of categories have been made for waters in lakes as well as waters upstream of lakes.
In addition to these instream or inlake protection values, EPA proposes to institute TN and TP downstream protection values (DPVs) for waters upstream of lakes. These criteria are yet to be determined, but will be set for waters upstream of each individual lake at values that will allow the downstream lakes to maintain their protection values.
A provision in EPA’s criteria is included that will allow for development of individual SSAC, such as was done for the Everglades. The effort required to justify such alternative criteria is complicated and lengthy and requires biological/chemical and physical assessments that some may consider not worth the effort.
EPA extended the effective date for the rule implementation for an additional 15 months to allow cities, towns, businesses, and other stakeholders, as well as FDEP, a greater opportunity to review the standards and develop flexible strategies for compliance.
Why Are These Values Problematic?
Waterbody Classifications. FDEP has four active classifications for waterbodies: I Potable Water, II Shellfish Harvesting, III Recreation, and IV Agricultural. The vast majority of Florida waters are Class III because any waterbody not Class I, II, or IV is automatically Class III. When setting violation levels and total maximum daily load (TMDL) criteria, the existing use of a narrative standard gives FDEP flexibility to account for the highly variable nature of the many waterbodies in the state. However, an artificial system used only for stormwater conveyance is treated the same as a natural system under the current rule. A system of open channels and storm drain pipes in series becomes, in FDEP’s view, a series of Class III waters connected by culverts, which should meet Class III criteria.
|a Platinum cobalt units (PCU) assessed as true color free from turbidity
b Chlorophyll a is defined as corrected chlorophyll, or the concentration of chlorophyll a remaining after the chlorophyll degradation product, phaeophytin a, has been subtracted from the uncorrected chlorophyll a measurement.
c Long-term color > 40 PCU
d Long-term color < 40 PCU and alkalinity > 20 mg/L CaCO3
e Long-term color < 40 PCU and alkalinity < 20 mg/L CaCO3
* For a given waterbody, the annual geometric mean of chlorophyll a, TN, or TP concentrations shall not exceed the applicable criterion concentration more than once in a three-year period.
EPA does not set waterbody classifications; however, EPA’s criteria require that Class III waters must comply with NNC concentration levels, regardless of whether they are manmade conveyances (e.g., concrete canal or roadside ditch) or natural streams.
In recent years, TMDLs have caused FDEP to struggle with classification and impairment issues. It has especially not wanted to remove canals and roadside ditches from Class III designation and impairment listings. Rules proposed to address some of these issues did not pass in the last legislative session. FDEP is now faced with EPA’s new standard requiring all Class III waters to meet NNC values, instead of the narrative criteria.
Clearly, what is needed are revisions to F.A.C. 62-302 that would create a separate category for manmade conveyance systems.
Protection Value Calculations and Levels. EPA’s criteria for protection value calculations and levels are problematic for several reasons. EPA and FDEP disagree on models and methodologies to be used to set the NNC values. For example, FDEP believes TN and TP values from pristine wetlands and streams should be the lower-limit reference values. However, some of the protection values selected by EPA are lower-than-pristine values and are not achievable with current technology.
South Florida Canals. Another major disagreement between FDEP and EPA is the need to set separate criteria for south Florida canals. FDEP believes there is insufficient scientific data at this time to set south Florida canal values.
Wastewater Treatment Plants. With regard to wastewater treatment plants (WWTPs), EPA’s NNC levels are lower than FDEP’s discharge limits set for advanced wastewater treatment plants and do not allow for mixing zones. Upgrading WWTPs for compliance with NNC values will be extremely expensive.
TMDL Impairment Levels. FDEP is currently setting TMDLs for many waterbodies listed as impaired. FDEP will now be required to use NNC values to determine impairment status, rather than previously calculated impairment or background values. Many waterbodies on FDEP’s verified unimpaired list will now be considered impaired and will fall into TMDL regulation, leading to expensive compliance programs by impacted communities.
Where Is a Downstream Protection Value Measured?
A DPV concerns waters upstream of a lake. How far upstream should the TN and TP concentration be measured? At the stream entrance to the lake? At the outfall from a subdivision pipe? At the entrance to a subdivision pond? It is yet to be determined.
How Will NNC Affect TMDLs?
FDEP will, in all likelihood, use the TMDL program for enforcing NNC. FDEP will probably be required to use NNC protection values for setting TMDL allocations and compliance. Yet, other EPA regulations require FDEP to use annual mass loadings as the basis for TMDLs. How shall FDEP resolve these conflicting methodologies? It is yet to be determined.
How Will NNC Affect Water Management District Permitting for New Development?
Florida is divided into five water management districts that issue stormwater permits for new development. Each district uses different stormwater design criteria based upon regional and geographical variations within a district. Instead of district-wide regulations, individual watersheds may have a different design criteria based on each waterbody’s lake, stream, or downstream protection value. FDEP has proposed that each district “adjust” its design criteria when implementing each new TMDL. How will this play out in light of NNC with another set of design criteria? It is yet to be determined. Will DPVs mean permitting criteria for land on a lake be different than for land upstream of a lake? Probably, but yet to be determined.
What BMPs Should Be Used to Meet Downstream Protection Values?
At this point, no single BMP can meet most DPV concentrations. Even with treatment trains, it will be difficult to meet DPVs, especially with the high groundwater levels and/or poorly draining soils found in much of Florida.
How Will Numeric Nutrient Criteria Affect Municipalities?
Many cities have municipal separate stormwater systems (MS4s) that collect and discharge stormwater runoff into surface waters. EPA’s proposed rule will affect municipalities that operate MS4s as well as wastewater treatment facilities. Upon renewal of MS4 or WWTP permits, entities will be required to meet more stringent limits for discharges. EPA estimates that 85 WWTPs in Florida would require upgrading to meet NNC criteria.
In addition, each municipality will be required to develop its own plan(s) for TMDL compliance. Depending on a site’s NNC criteria, new development may be required to design for stormwater discharge concentrations lower than predevelopment discharge concentrations. A community will most certainly have to retrofit older development to reduce nutrient levels. Some MS4s have considered requiring new development to overdesign their treatment systems to overcompensate for the community’s inability to fund retrofits of older systems. No matter what plan is chosen, the costs to taxpayers will increase.
How Will FDEP Enforce Compliance?
FDEP currently requires a community to monitor its WWTP discharges to demonstrate NPDES compliance. At this point, FDEP does not require MS4s to monitor stormwater discharges to demonstrate effluent concentration levels. This is very likely to change, but has yet to be determined. Grab sampling (ambient or storm event) is not difficult and is relatively inexpensive but has low accuracy. The next step up to achieve accurate sampling with autosamplers is difficult and expensive.
What Should a Community Do?
EPA’s water-quality goals will be challenging to meet. At this point, EPA has finalized its rules, but has not provided insight on how these rules should be implemented. FDEP has been given 15 months to develop a compliance plan. In the case of wastewater disposal systems such as sewage treatment plants and septic tanks, technology exists to achieve further reduction of nutrients from these sources, although the economic and political costs are high—as evidenced by recent controversial legislation for improved septic tank standards. For other sources of pollution, the answers are not as clear.
Most communities will receive TMDL designations and be required to meet NNC criteria. The question is when? A TMDL community should continue to develop masterplans to build stormwater retrofit projects. Regardless of the number of retrofit projects already identified, more will be required. Whatever a community’s stormwater utility fee or funding level is now, it will not be sufficient to meet compliance costs for NNC rules. Long-term planning and stormwater program enhancement will be key ingredients to meeting the numeric nutrient criteria and TMDL requirements in the future.
Will There Be More NNC Litigation?
Yes! There have been several lawsuits filed already, and more will follow.
Author's Bio: Gordon England, P.E., D.WRE, is president of Stormwater Solutions in Cocoa Beach, FL.